New theory of sun’s role in the origins of water on Earth

By Melissa Coade

November 30, 2021

asteroid heading towards the sun
Handout image issued by Curtin University of the sun, solar winds and itokawa. (Curtin University/PA Wire)

New research has shed light on the mystery of where Earth’s water originated, identifying the Sun as a ‘surprising’ likely source.

Scientists have analysed fragments of a near-Earth asteroid known as Itokawa to develop a solar wind theory about where the planet’s water came from.

The findings of an international team of scientists led by the University of Glasgow suggest that during the early days of the Solar System, solar wind created water on the surface of dust grains that was carried on asteroids and then crashed into Earth. 

The theory supposes that the solar wind comprised charged particles from the Sun largely made of hydrogen ions. 

Curtin University’s Space Science and Technology Centre (SSTC) director Professor Phil Bland explained that the theory was based on a meticulous atom-by-atom analysis of minuscule fragments of Itokawa, samples of which were collected by the Japanese space probe Hayabusa and returned to Earth in 2010.

“Our world-class atom probe tomography system allowed us to take an incredibly detailed look inside the first 50 nanometres or so of the surface of Itokawa dust grains, which we found contained enough water that, if scaled up, would amount to about 20 litres for every cubic metre of rock,” Bland said. 

Water covers 70% of the Earth’s surface — making it comparatively water-rich to other similar rocky-planets in the Solar System and for years scientists have puzzled over where it all came from.

The standing theory about Earth’s water origins before this latest discovery was that the water was carried to our planet in the final stages of its formation on C-type asteroids. However when the isotopic ‘fingerprint’ of these asteroids was tested, scientists learned that, on average, they did not match with the water found on Earth — this meant at least one other unaccounted for source for the water remained.

“Our research suggests the solar wind created water on the surface of tiny dust grains and this isotopically lighter water likely provided the remainder of the Earth’s water,” Bland said.

The international study was led by the University of Glasgow and was published in the journal Nature Astronomy this week.

According to another co-author Dr Luke Daly, the research findings will also help future missions as the question of how astronauts can access sufficient water without carrying supplies remains a barrier to future space exploration. 

“Our research shows that the same space weathering process which created water on Itokawa likely occurred on other airless planets, meaning astronauts may be able to process fresh supplies of water straight from the dust on a planet’s surface, such as the moon,” Daly said. 

The research was supported by funding from the Science and Technologies Facilities Council (part of UKRI), and conducted by researchers from the University of Glasgow, Curtin University, the University of Sydney, the University of Oxford, the University of Hawai‘i at Mānoa, the Natural History Museum, Idaho National Laboratory, Lockheed Martin, Sandia National Laboratories, NASA Johnson Space Center, the University of Virginia, Northern Arizona University and Purdue University.


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